Dose-Response Characteristics of the Alcohol Biomarker Phosphatidylethanol (PEth)-A Study of Outpatients in Treatment for Reduced Drinking

Aim: Measurement of whole-blood phosphatidylethanol (PEth) offers high sensitivity and specificity as alcohol biomarker. A remaining issue of importance for the routine application is to better establish the relationship between PEth concentration and amount and duration of drinking. Methods: The study included 36 subjects (32-83 years) voluntarily attending outpatient treatment for reduced drinking. At similar to 3- to 4-week intervals, they provided a diary on their daily alcohol intake and gave blood samples for measurement of PEth and carbohydrate-deficient transferrin (CDT). Whole-blood PEth 16:0/18:1 was measured by liquid chromatography-tandem mass spectrometry and serum CDT (%disialotransferrin) by high-performance liquid chromatography. Results: At start, the self-reported past 2-week alcohol intake ranged 0-1260 (median 330) g ethanol, the PEth 16:0/18:1 concentration ranged 0.05-1.20 (median 0.23) mu mol/L, and the CDT value ranged 0.7-13.0% (median 1.5%). At the final sampling after 5-20 (median 12) weeks, neither reported alcohol intake nor PEth and CDT levels differed significantly from the starting values. The PEth concentration showed best association with past 2-week drinking, followed by for intake in the next last week. The changes in PEth concentration vs past 2-week alcohol intake between two successive tests revealed that an increased ethanol intake by similar to 20 g/day elevated the PEth concentration by on average similar to 0.10 mu mol/L, and vice versa for decreased drinking. Conclusions: The PEth concentration correlated well with past weeks alcohol intake, albeit with a large inter-individual scatter. This indicates that it is possible to make only approximate estimates of drinking based on a single PEth value, implying risk for misclassification between moderate and heavy drinking.